A variety of lubricant oils are available having various total base numbers. One reason for having a total base number above zero in a lubricant is that acidic products are more likely to cause corrosion and wear to metal parts of a device than bases, which tend not to be involved in corrosion. Thus lubricants are formulated with sufficient excess base that over their intended lifetime, they remain neutral or slightly basic.
One particular use of a lubricant with a high total base number is in marine diesel applications which economically burn residual fuels with a sulfur content up to about 4.5 weight percent. Due to the high amount of sulfur containing species in the economical residual fuel, the combustion products include high amount of acidic SOx which causes additional wear to the cylinder wall and the rings of the piston. A solution to this lubrication/corrosion problem caused by the SOx is to include excess base in the lubricant oil so that the SOx is converted to a metal salt of the acid, which has less tendency to cause corrosion or wear. In many marine diesel applications the cylinder oil is injected near the rings of the piston on a continual basis to provide both continued lubrication and replace the base lost to neutralization. In these applications the cylinder lubricant is continuously consumed rather than returned to a sump. The marine diesel lubricant also needs good lubricity, dispersancy, oxidative stability and antiwear properties.
Traditional marine diesel lubricant formulations used overbased metals (detergents) for acid neutralization. Preparing basic complexes from oil soluble acids, bases, and acidic gases are described in U.S. Pat. Nos. 2,616,904; 2,616,905; 2,695,910; and 2,739,125. These patents typically attribute the ability to include high amounts of base in a form suitable for lubrication and stable against aggregation to complexes formed with various reaction procedures and promoters, sometimes including water and sometimes not, and of the chemical reaction between the base and the CO2 in the oil. They often quote a high basic metal content or ratio as an indication of preparing a useful complex.
GB 789,920 describes stable dispersions of inorganic metal compounds in lubricating oil and methods of making the same. Such compositions possessing increased detergency and increase reserve basicity find utility as additives in lubricating oils and possibly as corrosion inhibitors. The oil soluble surface active agents are typically sulfonates and the compositions include an aliphatic alcohol having less than six carbon atoms, which is removed. It appears that a mutual solvent for the alcohol and the lubricating oil, such as benzene, is used to form a homogeneous mass that later separate into phases when the benzene and alcohol are removed.
Emulsions of water in oil have been described for use in hydraulic applications such as in U.S. Pat. Nos. 3,269,946; 3,281,356; 3,311,561; and 3,378,494 where fire resistance was provided by the high water content of the fluid and the use temperature was low enough that the water of the water in oil emulsion was not readily evaporated. Water in oil emulsions were generally not desired in engine oils as discussed in column 1 of U.S. Pat. No. 3,509,052, lines 41-55, where a mayonnaise-like sludge was observed in the rocker arm covers and oil fill caps of smaller car engines when moisture condensed from the air and was emulsified into the engine oil.
Water in oil emulsions are also used as liquid fuels in some patent applications such as U.S. Pat. No. 4,002,435. An water in oil emulsion is described therein comprising a hydrocarbon, water, a water-soluble alcohol, and a novel combination of surface-active agents to provide a clear fuel, which is stable against phase separation.